A tandem polymerization strategy has been applied to the synthesis of novel core shell soft nanoparticles having tunable thermosensitivity. These nanoparticles have amphiphilic dendritic core shell structures, containing dendritic polyethylene (PE) as the hydrophobic core and a layer of poly(oligo((ethylene glycol) methacrylate)s (poly(OEGMA)s) as the hydrophilic shell. The dendritic PE core was first synthesized by chain walking polymerization, which was subsequently grafted with multiple poly(OEGMA) arms by atom transfer radical polymerization (ATRP) of OEGMAs. By varying the composition of the poly(OEGMA) grafts, the thermosensitivity of the core shell nanoparticles can be tuned with the lower critical solution temperature (LCST) temperature ranging from 20 to 60 degrees C. Taking advantage of the thermosensitivity and amphiphilicity, the synthesized core shell nanoparticles show interesting thermosensitive encapsulation of hydrophobic small molecules, which can be utilized for efficient separation of hydrophobic compounds from aqueous solution. This unique type of core shell nanoparticles may find potential applications in drug formulation and delivery, water treatment, and other nanotechnology applications.